Field of the Invention
This invention relates to a method of preparing bis(trifluoromethyl) disulfide by contacting, in the gaseous state, 2,2,4,4-tetrakis(trifluoromethyl)-1,3-dithietane with activated carbon at elevated temperature.
Bis(trifluoromethyl) disulfide, a known compound (bp 34.degree. C.), is an intermediate useful for the preparation of compounds containing trifluoromethylthio group, such as the fungicide bis(trifluoromethylthio) mercury.
C. T. Tuilock et al. in J. Org Chem., 25, 2016 (1960) disclose preparation of bis(trifluoromethyl) disulfide by liquid phase fluorination of trichloromethyl sulfenylchloride with sodium fluoride at 200.degree.-250.degree. C. in the presence of an organic solvent such as tetramethylene sulfone. R. E. Banks et al. in Advances in Inorganic Chem., 3, 414 (1961) disclose preparation of bis(trifluoromethyl) disulfide by reaction of iodine pentafluoride with carbon disulfide at autogeneous pressures and at temperatures of 200.degree. C., without a solvent. However, these prior art preparations are limited to liquid phase, batch operation which provide commercially unacceptably low conversion of costly reactants and commercially unacceptable low yields of bis(trifluoromethyl) disulfide.
Accordingly, it is an object of the present invention to provide a method for preparing bis(trifluoromethyl) disulfide, in the gas phase without solvent or diluent, from a readily available starting material.
It is a further object of the present invention to provide a continuous method for preparing bis(trifluoromethyl) disulfide, in the gas phase, in the presence of a inexpensive solid catalyst with commercially acceptable yield and commercially acceptable conversion rates of a readily available starting material.